The Gut and the Big Five Personality Traits

The five-factor model is a framework that defines universal personality dimensions using five core traits (OCEAN): openness, conscientiousness, extraversion, agreeableness, and neuroticism. Research suggests that around 50 percent of personality is hereditary, with social and environmental factors accounting for the remaining influence. The Big Five test is freely accessible at

Neuroticism, in particular, is linked to psychological vulnerability and an increased risk of health issues. A recent study during the COVID pandemic found that while neuroticism is associated with anxiety and depression, metacognitive strategies play a more significant role in emotional well-being.

In this article, we explore another tool for influencing neuroticism and managing mental health issues through the gut-brain connection.

Personality and the Gut Microbiome

In a recent observational study published in Brain, Behavior, and Immunity, researchers examined 672 adults (aged 23 to 69) and discovered significant differences in the diversity and composition of the gut microbiome based on the Big Five personality traits.

Individuals scoring higher in neuroticism showed elevated levels of the bacterial class gammaproteobacteria, which includes potential pathogens. These elevations were also observed in individuals scoring lower in conscientiousness, a trait associated with motivation and self-discipline.

The study also identified HPA axis activation and increased inflammatory markers in these individuals. Additionally, increased gut barrier permeability and the presence of bacterial toxins may play a role in the physiology of neuroticism.

Another study in the Human Microbiome Journal explored how gut microbes can impact personality traits through various pathways, including neural, immune, endocrine, and neurotransmitter systems. This study involved 655 adults and found that increased anxiety, stress, and decreased sleep quality were associated with changes in microbiome composition and reduced diversity.

Specific bacterial genera were linked to distinct behavioral traits, such as Bacteroides strains associated with the production of the neurotransmitter GABA, important for stress and depression management. Other findings included associations between gut bacteria prevalence and sociability or neuroticism levels.

The study did not find strong correlations between common probiotic species or strains and personality traits, emphasizing that the behavioral effects of these species are strain-specific. Interestingly, while the study found a positive link between mental well-being and diets rich in probiotic and prebiotic foods, it did not find a similar correlation with people taking probiotic supplements.

Seeding the Gut, Feeding the Mind

The lack of positive correlations with supplemental probiotics may be due to individuals with lower gut diversity and higher disturbances being more likely to take supplements. The author suggests that strain-specific mechanisms play a crucial role in effectiveness.

While maintaining healthy gut diversity is best achieved through a diet rich in probiotic and prebiotic foods, careful selection of high-performance probiotic formulations can be beneficial. Some of these formulations, known as psychobiotics, demonstrated clinical efficacy in improving mood, memory, cognition, and potentially influencing the Big Five personality traits positively.

However, it’s essential to choose probiotics with human clinical evidence supporting the final formulation, not just individual strains, to increase the likelihood of experiencing desired outcomes.